Toothpaste formulations generally contain dentally acceptable abrasive, humectant, water, and water-soluble polymer which serves as a thickener and binder for the ingredients. A variety of other ingredients such as flavors, sweeteners, preservatives and fluoride are also utilized at low levels. Glycerin and sorbitol are the most commonly used humectants for toothpaste, and depending on the characteristics desired in the product, polyethylene glycol or polypropylene glycol may be incorporated as well. Two types of toothpaste are widely produced: 1) cream or opaque; and 2) transparent or translucent gel.
The most commonly used thickeners or binders for toothpaste are carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC). Carrageenan, xanthan and polyacrylates are also used, but much less widely.
In the manufacturing process for toothpastes, incorporation of the dry water-soluble binder polymer into the composition often presents difficulties because of the tendency for lump formation when the dry polymers are added to and dispersed in aqueous systems. Attempts to avoid this problem have resulted in several typical procedures for toothpaste manufacture. In the first, the binder is predispersed in a non-solvent (glycerin is preferred to wet out the binder), and then a sorbitol/water mixture is added with vigorous agitation. If there is no (or only a low level of) glycerin or other water-miscible organic liquid in the formulation, then all the available sorbitol is used with as much free water as possible with vigorous agitation. In the second method, the binder is dry blended with other dry materials in the formulation, e.g. abrasive, and then the resulting blend is dispersed in the liquid ingredients with strong agitation. To obtain a good dispersion the binder should be less than about 20% of the total dry blend. In this method it is important to avoid blending the binder with materials that compete for water, e.g., salts or sweeteners.
These dispersion techniques are very time consuming. Consequently, there is a need in the industry for methods of incorporating water-soluble binder polymers which lead to lump-free products, rapid viscosity development and reduced batch preparation time, and which allow convenient handling of the binder.
U.S. Pat. No. 3,574,824 discloses an anhydrous toothpaste base having the following ingredients: an oil, such as mineral oil or vegetable oil, with a viscosity of 100 to 300 cps; a combination of polyethylene glycols having a viscosity of 2,200 to 3,400 cps with molecular weights of 550 to 6,000; a non-toxic and non-ionic emulsifier; at least one binding agent; and a compound having a negative heat of hydration. Binding agents disclosed are polyvinylpyrrolidone, colloidal magnesium aluminum silicate, gum acacia, sodium alginate, extract of Irish moss, carboxymethyl cellulose and methyl cellulose. Hexahydric alcohols, in particular mannitol and inositol, are disclosed as compounds having a negative heat of hydration.
U.S. Pat. No. 5,192,529 teaches a dentifrice composition that contains a polyol humectant, abrasive, and a thickener system consisting of low viscosity sodium carboxymethyl cellulose and low viscosity hydroxyethyl cellulose.
U.K. Patent No. 1,363,182 discloses a transparent or translucent gel toothpaste composition comprising polyethylene glycol having molecular weight below 700, and hydrated silica gel polishing agent having a specific surface area below 600 m.sup.2 /g. The composition may be thickened with carboxymethyl cellulose.
None of the aforementioned references discloses the use of fluidized polymer suspensions in toothpastes.